Revert "drm/amdgpu: remove TOPDOWN flags when allocating VRAM in large bar system"

This reverts commit c1055186.

This patch disables the TOPDOWN flag for APU and few dGPU cards
which has the VRAM size equal to the BAR size.

When we enable the TOPDOWN flag, we get the free blocks at
the highest available memory region and we don't split the
lower order blocks. This change is required to keep off
the fragmentation related issues particularly in ASIC
which has VRAM space <= 500MiB

Hence, we are reverting this patch.

Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2270


Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org